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For example, a parent class, A, can have two subclasses B and C. Both B and C's parent class is A, but B and C are two separate subclasses. Hybrid inheritance Hybrid inheritance is when a mix of two or more of the above types of inheritance occurs. An example of this is when a class A has a subclass B which has two subclasses, C and D.
The concept of class hierarchy in computer science is very similar to taxonomy, the classifications of species. The relationships are specified in the science of object-oriented design and object interface standards defined by popular use, language designers ( Java , C++ , Smalltalk , Visual Prolog ) and standards committees for software design ...
Other approaches include multiple inheritance and mixins, but these have drawbacks: the behavior of the code may unexpectedly change if the order in which the mixins are applied is altered, or if new methods are added to the parent classes or mixins. Traits solve these problems by allowing classes to use the trait and get the desired behavior.
The doctrine of composition over inheritance advocates implementing has-a relationships using composition instead of inheritance. For example, instead of inheriting from class Person, class Employee could give each Employee object an internal Person object, which it then has the opportunity to hide from external code even if class Person has ...
Also, another common example is that a person object created from a child class cannot become an object of parent class because a child class and a parent class inherit a person class but class-based languages mostly do not allow to change the kind of class of the object at runtime. For class-based languages, this restriction is essential in ...
Composition over inheritance (or composite reuse principle) in object-oriented programming (OOP) is the principle that classes should favor polymorphic behavior and code reuse by their composition (by containing instances of other classes that implement the desired functionality) over inheritance from a base or parent class. [2]
In comparison, a "class" is an abstract thing, in which objects can belong. For example, all kilogram-objects are in the class of KilogramObject, which might be a subclass of MetricObject, and so on. Prototypal inheritance in JavaScript is described by Douglas Crockford as You make prototype objects, and then … make new instances.
Not all languages support multiple inheritance. For example, Java allows a class to implement multiple interfaces, but only inherit from one class. [22] If multiple inheritance is allowed, the hierarchy is a directed acyclic graph (or DAG for short), otherwise it is a tree. The hierarchy has classes as nodes and inheritance relationships as links.